Known color measuring devices usually contain an arrangement for illuminating the measurement object to be measured, a pick-up arrangement for detecting the measurement light reflected back from the measurement object and converting the detected measurement light into corresponding electric signals, and an electronic system for evaluating the electric signals and for controlling the operating sequence of the measuring device. The illuminating arrangement may be designed to generate white light or colored light. The converter arrangement may comprise a number of color filters or dispersive elements, e.g. a diffraction grating, for splitting the measurement light into different wavelength ranges. Photodiodes or CCD converter systems may be provided for the actual conversion into signals.
These known color measuring devices are designed for measuring flat, smooth surfaces at least in the measurement range, where they deliver satisfactory results. However, when it comes to measuring or detecting the colors of measurement objects with a structured surface (textures), these color measuring devices usually fail because the measurement results can be distorted by the surface structure of the measurement object. Depending on how pronounced the surface texture is, the illuminating light can create gloss effects and/or shadowing effects which adversely affect the measurement and lead to an incorrect color result.
Another problem arises if a measurement object has two or more colors at the measuring point of interest and the intention is to determine all the colors. This objective can not usually be achieved at all with known, conventional color measuring devices.